[Shikijin]

Spoiler for Kizumonogatari:

1) So basically, Oshino took the heart from Kiss-Shot to bring balance, to make the fight between the three, and her 50-50. He said it should have ended with her dying but then Araragi came, so it's basically a reset. But I don't get why he returned the heart?

Because Kissshot wanted to turn back Araragi into a human, and it seems she couldn't have done it without having a complete body, so she needed her heart. For the same reason Guillotinecutter returned Kissshot's arms.

In short, by turning back Araragi into a human Kissshot was going to die, and Oshino thought that was better for humans, so he had no problems giving back the heart.

2) For the fight with Guillotinecutter, as far as I can remember, the conditions for one to win was by making the other party surrender. However, I remember Oshino saying to Araragi to give up his humanity? What does that mean?

That part was hard to translate. The concept is that Araragi had to give up his identity as a human, that is to accept he is a vampire and that therefore he can do the things vampires do and humans can't, namely to shape-shift the form of his arms.

One last thing, Kiss-shot went to find a place to die right? However when those three fought with her, the dice favored them, and they took out her limbs. She was at the verge of dying but then she realized she can't just die like that, and she met Araragi, turning him into a subordinate to gather back her limbs and gain back her power, and turn Araragi into a human again by killing her. She thought this could be her atonement for not turning back her first subordinate into a human, and finally find a place to die. Is this what happened?

Basically Kissshot wanted to die, but she when the time came she couldn't, she clinged to her life. The meeting with Araragi happened by chance, she thought he was gallant and spared his life, but in the end she still wanted to die. She thought of turning back Araragi into a human as an atonement, but that was not the original plan. Originally it seems she just planned to get killed by vampire hunters or something like that.